The present invention relates to an electric wave absorber used in an electric wave dark room, an electric wave absorbing wall, etc.
In recent years, use of electric waves has been spread rapidly in the field of mobile communication the like to realize a high-grade information oriented society. On the other hand, various electronic appliances have been popularized with the reformative advance of today's microelectronics technology. With the advance of such information communication technology, however, the influence of unnecessary electromagnetic noise on apparatuses relevant to precision machinery has become a subject of discussion.
An electric wave dark room (electric wave anechoic room) having no electromagnetic wave reflection is used for measurement of electromagnetic noise. An electric wave absorber is disposed in an inner wall of such an electric wave dark room. Examples of the background-art electric wave absorber used in the electric wave dark room include electric wave absorbers made from organic materials such as foamed styrol, foamed styrene, foamed urethane, etc., mixed with carbon black, or the like, to obtain electrical conductivity.
With the increase of electric wave interference, however, a large electric power test such as an immunity test, or the like, has been intended as a matter of duty. In the electric wave dark room used in a closed state, a nonflammable material needs to be used in terms of improvement of safety.
An example of the nonflammable electric wave absorber include a molded material containing inorganic grains, comparatively low in raw material cost and having a large number of closed cells, such as SHIRASU balloons, glass beads, perlite, etc., and carbon black which are integrally bonded by a heat-resistant inorganic adhesive agent such as water-glass (Japanese Patent No. 2743227).
The aforementioned electric wave absorber is, however, low in mechanical strength. There is a problem that the occurrence of breaking, the generation of dust upon collision, etc. cannot be avoided when, for example, the electric wave absorber is provided as a quadrangular pyramid- or wedge-shaped large-size structure which is about 100 cm high.